Lecture 21 Population Growth & Regulation

Question 1

Population Growth

Answer 1

slide 3-4

Question 2

Exponential Growth

Answer 2

slide 5-11

Question 3

Human Population Growth

Answer 3

slide 12-13

Question 4

Human Population Growth: Malthus

Answer 4

• 1798: Thomas Malthus analyzed human population
  growth and realizes it is exponential
• Showed that food production could not keep pace
  with population growth
• Projected that famine and disease would force the
  human population to curb growth unless birth rates
  decreased
• Human population growth often referred to as
  “Malthusian” growth or catastrophe
• Ideas inspired Darwin & Wallace

slide 14

Question 5

Human Population Growth

Answer 5

Was Malthus wrong?
* Peak growth rate of humans was
only 2.2% (that is, r=0.022)!
* Global population is still growing
* But the rate of growth is slowing
(it is now ~0.9%)
* Projected human population leveling
off at 9.7 billion

Global population is transitioning to low birth and death rate
due to:
* Health care
* Sanitation
* Education
* Social change
* Agriculture

slide 15-16

Question 6

Carrying Capacity

Answer 6

• Exponential growth can’t
  continue indefinitely!
• Carrying capacity (K) is the
  maximum population size that
  can be supported by available
  resources
• Carrying capacity can be
  determined by many different
  limiting resources
• Common factors include:
  energy, shelter, refuge from
  threats, nutrient availability,
  water, suitable nesting sites,
  disease, waste accumulation

Question 7

Logistic Growth

Answer 7

• Logistic population growth models
  population growth that levels off as a
  population reaches carrying capacity
• As populations become larger:
• Individuals must obtain sufficient
  resources to reproduce, or per
  capita birth rate will decline
• Starvation or disease may
  increase, causing the per capita
  death rate to increase

slide 18-22

Question 8

Density-Independent Regulation

Answer 8

• Density independent birth and death rates do not change with population density
• All individuals of a population equally likely to be affected
• Outcome is the same regardless of population size
• Lead to erratic and abrupt population changes
• Density dependent birth and
  death rates change with
  population density
• Density dependence occurs
  because as the population grows:
• Availability of resources per
  individual decreases
• Risk of predation, disease, parasites
  increase

slide 23-24

Question 9

Density-Dependent Regulation: Competition

Answer 9

More individuals = more competition for resources

slide 25-28

Question 10

Density-Dependent Regulation: Intrinsic Factors

Answer 10

More individuals = physiological changes

• Increased social
  contact and crowding
  causes stress
• Hormonal changes
  suppress growth and
  reproductive function
• Stress suppresses
  immune function and
  increases disease
  vulnerability

slide 29

Question 11

Density-Dependent Regulation: Territoriality

Answer 11

• More individuals = more competition for space
• Territoriality secures sole access to resources

slide 30-31

Question 12

Density-Dependent Regulation: Disease

Answer 12

More individuals = increased likelihood of disease transmission

slide 32

Question 13

Density-Dependent Regulation: Toxic Wastes

Answer 13

More individuals = accumulating waste

slide 33

Question 14

Density-Dependent Regulation: Predation

Answer 14

More individuals = easier food for predators

slide 34

Question 15

Population Dynamics

Answer 15

Population dynamics describe the spatial and temporal variation in population size as a result of abiotic and biotic conditions

slide 35

Question 16

Lynx and Hare

Answer 16

slide 36-37